TW511143B - Method for forming GaN/AlN superlattice structure - Google Patents

Abstract

A method of fabricating a GaN/AlN superlattice structure in gallium nitride compound semiconductor materials and devices. The superlattice structure is formed upon the substrate and/or formed in the gallium nitride semiconductor structure. The proposed superlattice structure suppress the dislocation to improve the performance of gallium nitride based compound semiconductor.

Description

511143 V. Description of the invention α) #Scope of the invention The present invention relates to a method and a structure for fabricating a superlattice in a gallium nitride semiconductor device, and in particular, a method and a structure for growing a superlattice that can block the development of differential rows. # 发明 发明 Background, wide energy gap, high-strength chemical bonds have been actively developed in recent years to respond to power and high-temperature electronic components. Can not be made, most of the nitrogen has a considerable lattice mismatch of the base 1203? Sapphire), 6H-, silicon (Si) plate and stupid crystal row (Misfit element, its matching and thermal expansion, these strains The release of energy is a penetrating difference between these poorly-acting elements. The non-Dislocation structure of the lattice between the element and the cubic structure film is often a difference in heterogeneous expansion coefficients that can be produced in the element. Partial misalignment The discharge is caused by the microstructure of the device. These dislocations in the active region of the gallium nitride-based material have the advantages of direct energy gap junction and good radiation resistance. They are used in blue / green ~ ultraviolet light-emitting devices. Size gallium nitride wafer is still required for gallium semiconductor components. Adopt and gallium nitride board. Generally used are C-faced oxide (A carbonized (S i C), Kunhuasu (G a A s)) Xi (/ 5-SiC), etc. The strain caused by the base matching often causes dislocations). In addition, in the typical optoelectronic structure, because the crystal lattices between the wormworm boats are not different, it is easy to accumulate at the heterogeneous interface. Strain energy and use process Dislocations often form on the surface of the crystal, which is called the main cause of degradation. When they are degraded or lost, it is often clear that dislocation defects usually start on the heterogeneous interface. Produce

511143 V. Description of the invention (2) (Active Region), if there is a difference, it will become a trap (recombination centers) of minority carriers (Recombination Centers), thus affecting such semiconductor components Characteristics and quality. For example, for light-emitting elements, the existence of differential row defects causes excess carrier binding not to release energy in a light-emitting recombination mode, but instead uses a non-radiative recombination effect (Nonrad i at i ve Recombination Effect). Release energy.

In addition to providing traps to capture minority carriers, differential rows also provide short cuts for carrier concentration diffusion. For a component with a specific carrier distribution, the rapid diffusion of carriers along the delta or the segregation of the carriers near the differential row will cause the uneven distribution of the carrier of the component and affect the function of the component. Because there is no substrate with a lattice constant that is exactly matched to gallium nitride, heteroepitaxial growth is currently used when growing gallium nitride thin films. Taking the most commonly used C-plane oxidized substrate as an example, although the physical properties and chemical properties of the oxidized substrate are relatively stable, there is about 16% lattice mismatch between it and the gallium nitride film.

This causes the defect density of the gallium nitride film grown on the alumina substrate to be very high, and usually there are differential rows with a density of 10E11 ~ 10E9 / cm2 inside. In order to effectively reduce the difference in row density, researchers have developed many methods to solve this problem, such as: Lateral worm crystal (Latera 1 Epita X ia 1 Overgrowth) method, buffer layer structure, first on the substrate Low-temperature-growth aluminum nitride (A 1 N) or gallium nitride (G a N) serves as a buffer layer to alleviate the lattice mismatch between the epitaxial film and the substrate, thereby improving the subsequent growth of high-temperature gallium nitride. Stupid crystal quality, strained superlattice structure and intermediate-layer structure, etc.

Page 6 511143 V. Description of Invention (3) and so on. Even so, the differential row density of nitride materials generally used for ultra-high-brightness blue-green light-emitting diodes is still as high as 1 0 E 8 to 1 0 E 1 0 / c m 2. In recent years, Nakamura has used the ELOG (Epitaxial Lateral Overgrowth) method to produce blue light-emitting diodes with a lifespan of 10,000 hours. One of its major breakthroughs is the use of the so-called E L 0 G method to further reduce the density of penetrating differential rows. # 发明 Target's and Description

Therefore, if you want to manufacture high-quality gallium nitride semiconductor devices, it is very important to reduce the through-difference density in the gallium nitride epitaxial film. The object of the present invention is to propose a structure and method for growing a superlattice 'to reduce the differential density in a gallium nitride epitaxial film. The present invention utilizes a superlattice structure in which aluminum nitride / gallium nitride is added in the manufacturing process to block the through differential row and reduce the differential row density. The superlattice structure of aluminum nitride / gallium nitride can be divided into: (1) first grow the aluminum nitride / gallium nitride superlattice structure on the substrate and then grow the epitaxial compound of gallium nitride. (2) Grow an aluminum nitride / gallium nitride superlattice structure between two layers of gallium nitride compound epitaxy. In order to further explain the structure, manufacturing method and features of the present invention, it can be more clearly understood from the following detailed description and drawings.

#Detailed Description The structure of the present invention will be described below by taking the growth of nitrogen-titanium silicide crystals on a C-plane oxide substrate as an example. In the preferred embodiment, please refer to FIG. 1, a C-plane alumina-based

Page 7 511143 V. Description of the invention (4) A plate (labeled 10) on which a first layer of nitrogen (labeled 2 0) is grown. An aluminum buffer layer having a thickness of 100 to 300 nm Between; the second layer (labeled 30), which is grown on the first layer (labeled 20), is a superlattice structure of nitride / gallium nitride, and the thickness combination of aluminum nitride / gallium nitride is 4 ~ 7 nm / 4 ~ 7 nm,. The logarithm is between 3 and 20 pairs, and the total thickness is between 24 and 28 nm; the third layer (labeled 40) is grown on the aforementioned second layer (labeled 3 0) is a gallium nitride epitaxial layer. The superlattice structure shown in Figure 1 can be used to effectively block the development of differential discharge. Figure 2 is a cross-section transmission electron microscopy (TEM) photograph of a gallium nitride film with an ungrown aluminum nitride / gallium nitride superlattice structure. Figure 3 is a bottom grown aluminum nitride / gallium nitride. Cross-section transmission electron microscopy (TE) photograph of a gallium nitride thin film with a superlattice structure (10 pairs). Comparing Fig. 2 and Fig. 3, it clearly shows the aluminum nitride / gallium nitride supercrystal The lattice structure is very effective in blocking the development of the differential row. FIG. 4 is another preferred embodiment of the present invention. The superlattice structure of aluminum nitride / gallium nitride (labeled 60), and the thickness combination of aluminum nitride / gallium nitride is 4 ~ 7nm / 4 ~ 7nm. The logarithm is between 3 and 20 pairs, and the total thickness is between 24 and 280 nm. This aluminum nitride / gallium nitride superlattice structure (labeled 60) is grown between the lower gallium nitride compound dummy (labeled 50) and the upper gallium nitride compound dummy layer (labeled 70). Figure 5 is a cross-sectional transmission electron microscopy (TEM) photo of an aluminum nitride / gallium nitride (five pair) superlattice structure added to a gallium nitride epitaxial film. In this structure, nitrogen is clearly shown. The aluminum / gallium nitride super-φ lattice structure is also very effective in blocking the development of the differential discharge. FIG. 6 shows the aluminum nitride / gallium nitride superlattice structure of the preferred embodiment of the present invention. The epitaxial film interface in the structure will have biaxial strain.

Page 8 511143 V. Description of the invention (5) (Biaxial Strain), the gallium nitride film (labeled 80) will feel the biaxial compression (C ompressive) strain and nitride nitride film (labeled 9 0 ) Then feel the biaxial extension (Extensive) strain. The thickness of the gallium nitride film (labeled 80) and the thickness of the nitride film (labeled 90) both affect the effect of blocking the difference rows and cause new defects, such as misalignment rows, which in turn affects subsequent nitriding. The quality of the gallium epitaxial layer is evaluated by our experiments. The combination of nitride thickness and gallium nitride thickness is preferably 5 nm / 5 nm. Theoretically, the more the number of nitride / gallium nitride in the superlattice structure, the better the blocking effect, but considering the actual application requirements, production yield and cost considerations, a structure with three pairs to twenty pairs Better.

The aforementioned gallium nitride ferrite layer (labeled 40, 50, and 70) may be made of materials such as n-type GaN, AlGaN, InGaN, and AlGalnN. The material of the substrate (labeled 10) used for the gallium nitride semiconductor device is not limited to those cited in the foregoing preferred embodiments, and it also includes various materials with appropriate characteristics. {列 如 ·· 6 Η— 石炭4 dagger stone eve (S i C), Shishen 4 dagger # 家 (G a A s), Shi Xi (Si), and cubic structure silicon carbide (/ 3-S i C) and so on. In addition, the aluminum nitride buffer layer of the first layer (labeled 20) in Figure 1 may also be a gallium nitride buffer ^ 〇

The superlattice structure of aluminum nitride / gallium nitride in Figures 1 and 4 has a growth temperature boundary between 4 5 0 ~ 6 0 0 ° C or 9 0 0 ~ 1 2 0 0 ° C . Although the manufacturing method of the present invention uses the atomic layer (Atomic Layer Epitaxy) method, other deposition methods can also be used, such as metal organic chemical vapor deposition (MOCVD). , Molecular beam epitaxy (MBE) and so on.

511143 on page 9 5. Description of the invention (6) # Brief description of the drawing Figure 1 is a schematic structural diagram of one of the preferred embodiments of the present invention; Figure 2 is the underlying ungrown aluminum nitride / gallium nitride superlattice Cross-section transmission electron microscopy (TEM) photo of the structured gallium nitride thin film; Figure 3 is a cross-section of a gallium nitride thin film with a bottom-grown aluminum nitride / gallium nitride superlattice structure (SLS, 10 pairs) Cross-section transmission electron microscopy (TEM) photo; Figure 4 is a schematic structural view of another preferred embodiment of the present invention; Figure 5 is a method of adding aluminum nitride / nitride in the middle of a gallium nitride epitaxial film Cross-section transmission electron microscopy (TEM) photo of gallium (5 pairs) superlattice structure;

FIG. 6 is a schematic diagram of the aluminum nitride / gallium nitride superlattice structure of the present invention.

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Claims (1)

511143 VI. Application Patent Scope 1. A blocking structure for blocking the growth of differential rows in a gallium nitride semiconductor device, the blocking structure includes: (I) forming a first buffer layer on a substrate, which is made of aluminum nitride or nitride Formed of gallium; (Π) growing an aluminum nitride / gallium nitride superlattice structure on the first buffer layer. 2. For example, the barrier structure of the first patent application range, wherein in the aforementioned aluminum nitride / gallium nitride superlattice structure, the thickness composition range of the single-pair is 4 ~ 7nm / 4 ~ 7nm. 3. The rubidium resistive structure according to item 1 of the patent application range, wherein the logarithm of the aforementioned aluminum nitride / gallium nitride superlattice structure is 3 to 20 pairs. 4. A blocking structure for blocking the growth of a differential row in a gallium nitride semiconductor device. The blocking structure is an aluminum nitride / gallium nitride superlattice structure formed between two layers of gallium nitride compound insect crystals. 5. For example, the barrier structure of the fourth scope of the patent application, wherein, in the foregoing aluminum nitride / gallium nitride superlattice structure, the thickness range of the single-pair pair is 4 ~ 7nm / 4 ~ 7nm 〇6. The barrier structure of item 4 of the patent, wherein the logarithm of the aforementioned aluminum nitride / gallium nitride superlattice structure is 3 to 20 pairs. 7. If the barrier structure of the first or fourth item of the patent application scope, wherein the growth temperature boundary of the aforementioned aluminum nitride / gallium nitride superlattice structure is between 4 5 0 ~ 6 0 0 ° C or 9 0 0 ~ 1 2 0 0 QC. Page 11